Firewalls apply rules to block access by a client device to various network resources. In some instances, the firewall can obtain a domain name associated with a network request because the request either contains the domain name, or the request contains an Internet Protocol (IP) address that can be easily and accurately resolved into a domain name. However, when the request contains an IP address that does not readily resolve to a useful domain name, it can be difficult to apply security rules at the firewall that are domain-name based.
There remains a need for improved determination of a domain name based on an IP address for use in network security.